Before I started the FF8 voiceover project, I spent about a year working on a rules engine and game server/client for Magic: the Gathering. For legal reasons, it doesn't have online play or matchmaking. Multiplayer is only allowed on LAN. I did it for fun and for the challenge, and to get some exposure / resume fodder. The 3d engine is built on
JMonkeyEngine.
It's not as feature-filled as Forge (the one most people use), but it does support almost every card ever printed, and it even supports drafts.
There's a demo video and some pictures on its
documentation site.
I'm still looking for a job in the US, preferably in software development (especially for games), so if anybody works for a company that's hiring or knows someone in need of a good software engineer, maybe you can show them this